Centrifugal separator to free a liquid from both lighter particles and heavier particles

Abstract

In a centrifugal rotor having inlet channels (23) which are situated between a stack of axially separated conical separation discs (13) and the rotor end wall (10), against which the separation discs turn their apex ends, there is formed a counter pressure chamber (22) in an area where the inlet channels (23) communicate with one end of several distribution channels (21) extending through the stack of separation discs. The counter pressure chamber (22) is free of entrainment members, so that liquid leaving the inlet channels (23) is allowed to rotate in the counter pressure chamber at a smaller angular speed than the rotor. Furthermore, the counter pressure chamber (22), communicates with a radially outer part of the rotor separation chamber (9) through a space (35) situated outside a flow space (36), through which separated liquid is to flow from the interspaces between the separation discs to a number of outlet channels (27) in the vicinity of said rotor end wall (10).

What is claimed is: 
     
       1. A centrifugal separator for freeing a liquid from suspended light particles, which have a lower density than that of the liquid, and suspended heavy particles, which have a higher density than that of the liquid, said centrifugal separator having a rotor, which is arranged for rotation around a center axis (R) extending through the rotor comprising a rotor body (3-5), having a first end wall (10) and a second end wall (12) arranged axially each on one side of a separation chamber (9) surrounding the rotor axis (R), a central inlet (24) for said liquid containing the suspended light and heavy particles, a central first outlet (26) through said first end wall for liquid having been freed from light and heavy particles and a central second outlet (18) for a liquid light phase containing separated light particles,   a stack of conical separation discs (13) arranged in the separation chamber (9) in a way such that the separation discs (13) having base portions and apex portions and being arranged with interspaces between said discs are placed coaxially with the rotor and have said apex portions facing said first end wall (10),   a plurality of inlet channels (23), said channels being distributed around the axis (R) and connecting the central inlet (24) of the rotor body with the separation chamber (9), and having an inclination relative to the axis (R) in the same direction as a generatrix of each one of said conical separation discs (13),   the separation discs (13) having several series of aligned holes forming several parallel distribution channels (21) through said stack, said distribution channels communicating with the interspaces between the separation discs (13) and at the ends of said distribution channels situated closest to said first end wall (10) communicating with said inlet channels (23), and   a plurality of outlet channels (27), said outlet channels being distributed around the rotor axis (R) and intended for liquid having been freed from light and heavy particles, and having channel openings situated in the separation chamber (9) in the vicinity of the first end wall (10) and extending from said channel openings towards the rotor axis (R), wherein said inlet channels (23) open in a counter pressure chamber (22) extending around the rotor axis (R) and limited axially by chamber walls which are substantially free of rotational entraining members, so that liquid is allowed to rotate in the counter pressure chamber (22) at an angular speed lower than that of the rotor body (3-5),   further wherein the counter pressure chamber (22) has a first portion communicating with said distribution channels (21) and a second portion situated radially outside said first portion and communicting with at least one sludge passage (34), and   further wherein the at least one sludge passage (34) communicates with the separation chamber (9) in a part thereof so situated that separated heavy particles are allowed to move from the at least one sludge passage (34) radially outwardly in the separation chamber (9) through an area (35) thereof which is situated axially or radially or both outside a flow space (36) which surrounds the stack of separation discs (13) and through which liquid having been freed from suspended light particles has to flow on said liquid's way from the interspaces between the separation discs (13) to the openings of said outlet channels (27).     
     
     
       2. The centrifugal separator according to claim 1, in which the at least one sludge passage (34) opens in the separation chamber (9) at a level radially outside the stack of separation discs (13). 
     
     
       3. The centrifugal separator according to claim 1, in which the at least one sludge passage (34) opens in the separation chamber (9) at a level radially outside said channel openings. 
     
     
       4. The centrifugal separator according to claim 1, in which the at least one sludge passage (34) comprises a continuation raidally outwardly of said counter pressure chamber (22) and is substantially free of rotational entraining members. 
     
     
       5. The centrifugal separator according to claim 1, in which a conical partition (19) is arranged between said first end wall (10) and the stack of separation discs (13), the counter pressure chamber (22) being formed by and between the conical partition (19) and said first end wall (10). 
     
     
       6. The centrifugal separator according to claim 5, in which the conical partition (19) has through openings (20) through which said inlet channels (23) communicate with said distribution channels (21). 
     
     
       7. The centrifugal separator according to claim 5, in which the conical partition (19) extends radially outside the stack of separation discs (13) and is substantially smooth on a surface thereof, which surface is facing axially towards said flow space (36) radially outside and surrounding the stack of separation discs (13). 
     
     
       8. The centrifugal separator according to claim 7, in which said conical partition (19) delimits said outlet channels (27) and said outlet channel openings in the separation chamber (9). 
     
     
       9. The centrifugal separator according to claim 5, in which a portion (33) of the conical partition (19) extends a distance radially outside said channel openings in the area between said channel openings and said first end wall (10). 
     
     
       10. The centrifugal separator according to claim 9, in which said portion (33) of the conical partition (19) has a substantially smooth surface facing towards the separation chamber (9). 
     
     
       11. The centrifugal separator according to claim 1, in which the central inlet (24) of the rotor for liquid to be treated extends through said first end wall (10). 
     
     
       12. The centrifugal separator according to claim 1, in which said second outlet (18) of the rotor body, intended for said liquid light phase, extends through said second end wall (12).